You might want to watch this:
https://www.youtube.com/watch?v=uDqjIdI4bF4Hopefully it should start you at the beginning of the video.
Anyway, he needs to react to his arm's movement. You can't move a single body part without moving the rest of your body even a little bit. In this case, you're raising his centre of mass slightly, so his weight needs to shift to compensate - especially since his stance is extremely unstable.
A few other things I'd change:
His left arm is perfectly straight. In reality your arms' resting positions are always at least slightly bent. Plus the arm's split into two sections so it shouldn't look completely straight even if it's at its most extended. I also think the shoulder-to-wrist length is a little short. Not that there's much of a wrist to find in the first place.
Hands rest at the side of the body rather than in front, and the thumb usually points forwards while the fingers rest bend behind it. A good example is here:
https://c2.staticflickr.com/2/1407/4604646620_d078275296_z.jpgConsidering his weight, I'd recommend shifting his centre of mass downwards, possibly by making him slump a bit. in any case, he definitely needs surer footing. That's why Hulk's legs are always apart.